Our focus is on contact-induced gene expression in oral streptococci and the spatial organization of these bacteria, oral actinomyces and other oral bacteria in biofilm communities. Dental plaque is a biofilm community, which is characterized by a complex and highly organized set of interactions among oral bacteria as well as between bacteria and human oral tissue. This initiative is centered on the bacteria known to be early colonizers of a freshly cleaned tooth surface. They represent a significant portion of the bacterial activity in biofilms formed in the first four to eight hours in vitro on saliva-coated glass surfaces and in vivo on removable human enamel chips. We are also investigating the oral fusobacteria because they interact with the broadest variety of oral bacteria including early colonizers, late colonizers and potential periodontal pathogens and, therefore, are thought to be major contributors to dental plaque organization. The overall focus of this project is to investigate cell adherence molecules, cell signaling molecules, gene expression and gene transfer among bacteria within human oral biofilms and to relate these events to bacterial community architecture. Our long-range goal is to understand the molecular mechanisms of cellular communication and their relationship to the development and establishment of dental plaque and colonization of the host epithelial cells.